When Sir Charles died he left estate of £1,052,070 (equivalent to £493 million in 2007), making him one of the richest men in the country. He had nine children, and, at the time of his death, over fifty grandchildren.The enormous fortune and estates dwindled over the next 40 years.

The reasons for this are many: it was divided up among numerous children and grandchildren, some of whom were better at spending than making money;  external factors such as two world wars, increasing death duties, changes in energy needs and the nationalisation of the coal industry also took their toll. Sir Charles left the Brook estate to his youngest son, General Jack Seely MP, who was created Lord Mottistone in 1933.